Spring brake actuator with corrosion fuses

Abstract

A spring break actuator (10) with a cast aluminum adapter (74) partially defining tandem spring brake and service brake portions has several corrosion fuses on the adapter. Each corrosion fuse is defined by a recessed or thinned area which does not compromise the structural integrity of the adapter.

I claim: 
     
       1. In a brake actuator of the type having a housing with a wall formed of a material subject to corrosion, a pressure chamber within the housing, and a movable member within the housing movable in response to changes in normal pressure within the pressure chamber for actuation and release of a brake, the improvement comprising: at least one corrosion fuse on the housing adjacent to the pressure chamber, said corrosion fuse comprising a portion of the wall wherein the wall is thinner than the surrounding area, and the thinner wall portion has a clearly defined area of a dimension insufficient to compromise the ability of the wall to support the housing so that any corrosion occurring on a surface of the wall is likely to result in penetration of the wall at the thinner wall portion before penetration of the surrounding areas of the wall.   
     
     
       2. A brake actuator according to claim 1 wherein the thinner wall portion is formed by a depression on an exterior surface of the wall. 
     
     
       3. A brake actuator according to claim 2 wherein the depression is formed with curved edges that avoid discontinuities in the exterior surface of the wall. 
     
     
       4. A brake actuator according to claim 3 wherein the depression is circular in shape. 
     
     
       5. A brake actuator according to claim 4 wherein the number of corrosion fuses is within the range of two to ten, inclusive. 
     
     
       6. A brake actuator according to claim 1 wherein the thinner wall portion is formed with curved edges that avoid discontinuities in the surface of the wall. 
     
     
       7. A brake actuator according to claim 1 wherein the thinner wall portion is circular in shape. 
     
     
       8. A brake actuator according to claim 1 wherein the number of corrosion fuses is within the range of two to ten, inclusive. 
     
     
       9. In a brake actuator for a vehicle comprising: a service brake actuator and a spring brake actuator disposed in tandem and secured to each other by a metal adapter,   said adapter having a wall adjacent to a chamber adapted to receive pressurized fluid for moving an actuator rod in one of the service and spring actuators, the improvement comprising:   a corrosion fuse on the adapter defined by a portion of the wall wherein the wall is thinner than at the surrounding area, and the thinner wall portion has a clearly defined area of a dimension insufficient to compromise the ability of the wall to contain pressurized fluid within the chamber so that any corrosion occurring on a surface of the wall is likely to result in penetration of the wall at the thinner wall portion before penetration of the surrounding areas of the wall.   
     
     
       10. A brake actuator according to claim 9 wherein the thinner wall portion is formed by a depression on an exterior surface of the wall. 
     
     
       11. A brake actuator according to claim 10 wherein the depression is formed with curved edges that avoid discontinuities in the exterior surface of the wall. 
     
     
       12. A brake actuator according to claim 11 wherein the depression is circular in shape. 
     
     
       13. A brake actuator according to claim 12 wherein the number of corrosion fuses is within the range of two to ten, inclusive. 
     
     
       14. A brake actuator according to claim 9 wherein the thinner wall portion is formed with curved edges that avoid discontinuities in the surface of the wall. 
     
     
       15. A brake actuator according to claim 9 wherein the thinner wall portion is circular in shape. 
     
     
       16. A brake actuator according to claim 9 wherein the number of corrosion fuses is within the range of two to ten, inclusive.